If you're able to buy a diamond knife sharpener, you can run the knife several times through the course grain and then fine grain to get it to a finer edge. For upkeep on your knife before need for another sharpening, consider a ceramic honing rod. This will extend the sharpness of your blade until the next sharpening with the sharpener. Eventually it will go dull and you'll need a wetstone to sharpen it manually. Or just buy a new knife. With a sharp knife, it should never be difficult.